The present invention relates to a dielectric resonator and more particularly to a dielectric resonator provided on a microwave circuit board, the dielectric resonator defining mutually opposing planar surfaces and an outer peripheral surface extending between these planar surfaces and which resonates in the TE.sub.01.delta. mode, and a microstrip line to which the dielectric resonator is magnetically coupled.
Conventionally, a dielectric resonator of this type which resonates in the TE.sub.01.delta. mode is fixed on a microwave circuit board in the manner shown in FIG. 7.
In this figure, a dielectric resonator 11 is made of dielectric material and has a columnar shape defining mutually opposing planar surfaces 11a, 11b and an outer peripheral surface 11c extending between these planar surfaces 11a, 11b. The direction of a normal axis passing through these mutually opposing planar surfaces 11a, 11b is the one in which a microwave advances. A support block 12 is made of insulating material, and is fixed to one planar surface 11b of the dielectric resonator 111 with an adhesive or the like, and is also fixed on the top surface of a microwave circuit board 13 with an adhesive or the like. The dielectric resonator 11 is fixed in such a manner that its planar surfaces 11a, 11b are parallel to the plane of the microwave circuit board 13.
The microwave circuit board 13 is made of dielectric material and a microstrip line 14 is formed on its top surface while a ground conductor 15 is formed on its bottom surface. The dielectric resonator 11 is fixed in position close to the microstrip line 14.
In the structure described above, a magnetic field is formed in the direction of the normal axis passing through the mutually opposing planar surfaces 11a, 11b of the dielectric resonator 11, and as shown in FIG. 8, magnetic flux F, which forms the magnetic field, envelops the microstrip line 14.
Thus, the dielectric resonator 11 is magnetically coupled with the microstrip line 14, forming a resonance circuit. Therefore, adjusting the distance l between the dielectric resonator 11 and the microstrip line 14 allows the degree of their mutual coupling to be correspondingly adjusted, thus resulting in adjustments of resonance circuit characteristics.
In the prior art structure described above, the dielectric resonator 11 is raised to a specified height using the support block 12. This is because when the planar surfaces 11a, 11b of the dielectric resonator 11 are too close to the ground conductor 15 of the microwave circuit board 13, the rate of magnetic flux in contact with the ground conductor 15 increases, which in turn causes an increase in eddy-current loss, resulting in a decrease in a Q value of the resonance circuit.
Therefore, the support block 12 became indispensable, which brought about an increase in the number of members with the resultant increase in production costs and also with the necessity for fixing the support block 12 to the dielectric resonator 11, thus causing a problem of the production process being complicated.